1. Field of the Invention
The current invention is generally directed to improvements useful in gas-spring devices employed in, for example, two-wheeled vehicle suspension elements such as: shock absorbers, suspension forks and other variable-volume gas-pressurized devices (“gas springs”).
2. Description of the Related Art
As described in detail in the '144 application and summarized in the '403 application, the stiffness (force-versus-travel or, as used herein, “spring curve”) of a gas spring may be associated with “travel modes” (e.g. long and short). For example, as depicted in the two spring curves of FIG. 15 of the '144 application and described in para [0008] of the '144 application, travel modes are indicative of how far a spring compresses when subjected to a given compression force (i.e., a gas spring will compress more in long travel mode than in short travel mode). For example, for the gas spring described in the '144 application, in the long travel mode (FIG. 13), the amount of travel produced by a 750 pound force is approximately 1.75″. In the short travel mode (FIG. 14), the amount of travel produced by the same force is approximately 1.27″. Note that for the reasons described in para [0063] of the '144 application, all pressure values are close approximations and effected by the presence of the negative gas spring.
In the '144 application, selection between the long and short travel modes is easily accomplished on the fly by a rider making a small (e.g. ¼) turn of an adjustment knob and without all the disadvantages of prior art methods for changing travel length (see discussion of prior art in the '403 application). In the '144 application there are two gas chambers. The long travel mode is operative when the two gas chambers are in fluid communication with each other. The short travel mode is operative when the two gas chambers are not in fluid communication with each other.
Although the gas spring as shown in the '144 application is capable of producing two available travel modes, it is often desirable to have more than two available travel modes—as described in the '403 application. Furthermore, it may often be desirable for the short travel mode to produce a substantially shorter travel length than has been so far provided such that for a given force, the distance between the travel limits of the long and short travel modes are spaced further apart, e.g., approximately 50% or more, or in other words, the travel in the short travel mode is approximately 50% or less of the travel in the long travel mode.
Finally, in general, by providing a rider with the ability to control suspension travel, riders have a tool for controlling the stiffness of the gas spring and the magnitude of the force that would cause a harsh bottom-out and uncomfortable metal-to-metal contact. Furthermore, by providing rider with a wide range of travel mode options, the suspension can, for example, be optimized for: (a) more consistent tire contact patch (lower gas spring stiffness); (b) more comfortable ride (lower gas spring stiffness); (c) increased pedal efficiency (reduced pedal bob) (stiffer gas spring); and (d) reduced fore-aft pitching (stiffer gas spring).
Therefore, there is room for improvement within the art.